there is a heated debate on this but someone said in Jeorge Cervantes books he says to never cut fan leaves no matter what not unless the are under 50% green even. and thats good enough for me.
I also heard that the buds dont need much light they grow from the power that your fan leaves produce.
The way I look at it is that the plants main mission is to grow buds to reproduce so I would trust that the plant knows what its doing. but i guess tieing them back just incase wouldnt hurt as long as the fan leaf is still in good light.